This invention relates to seals for rotary shafts and more particularly to a dual lip integral seal which is installed in two pieces in a split housing which surrounds the shaft.
In environments such as gear cases and the like wherein one or more shafts enter the housing and wherein access must be available to the interior, the most practical way to install the gear case and seal the shafts is by the provision of half sections with a seal in each half section. A particular application in that of a diesel electric locomotive wherein power transfer is made from the traction motor to the wheels by way of a large set of spur gears. These gears must be kept lubricated with grease and since the gears must be meshed beforehand, the best way to accommodate the situation is to install the gear case in mating half sections.
Each half section of the gear case, in the past, contained channels adjacent the shaft openings and these channels were filled with packing material. The current and most popular form of packing is a metal-encased felt seal, the metal gripping the felt material and providing a support for placement in the channels. Since the environment is quite severe in that high surface speeds, high operating temperatures and moisture conditions are encountered these seals perform rather poorly and must be replaced frequently. The seals are subject to tearing and ripping and due to the high relative circumferential motion are particularly prone to bunching, all of which contribute to leakage and a high failure rate for the seals.
While such described seals are state of the art for locomotive applications, other forms of rotary seals are known in different environments. Thus, for example, U.S. Pat. No. 3,776,559 describes a shaft seal in which an elastomeric sealing section is combined with a backing member which may be metal or rigid plastic material. While a dual lip seal combined with a backing member is disclosed, as well as a split form of assembly, in this arrangement the seal and backing member grip the shaft and rotate with it, being guided at their periphery in an appropriately configured housing member.
U.S. Pat. No. 3,738,669 discloses a half seal arrangement consisting of an integral elastomeric seal and metal retainer member. This structure is a single lip seal in which each half of the seal is a mirror image of the mating half, and is arranged to be supported and to seal between radially spaced surfaces. The metal insert is fully surrounded by rubber to establish the fluid tight seal and care must be exercized so that the seal halves are properly oriented with respect to one another. In this seal a relatively wide base is used with the sealing lip lying between the axial dimension of the base.